In order to achieve the optimum grinding efficiency for a grinding mill, the mass of the charge load in the mill must be of a predetermined value which is dependent upon the run-of-mine for an autogeneous mill (i.e., the material entering the mill) or the grinding media for a ball, rod or pebble mill. Presently, no system has been developed which can reliably determine the charge load in the mill.
Attempts have been made in the past to relate the mill charge load to the bearing pressure of the trunnion bearing supporting the trunnion of the mill. One such attempt is disclosed in Canadian Pat. No. 791,424, issued Aug. 6, 1968 to Harris et al. These attempts have not been reliable, however, because the liner in the mill is continuously wearing, whereby the mill weight is constantly varying. Also, it should be understood that 40 to 60 percent of the loading, due to gravity, placed on the trunnion bearing, is due to the weight of the grinding mill. Hence, any reading taken of loading on the trunnion bearing, cannot be accurately measured and related to charge load in the mill, because fluctuations in the grinding mill weight are largely responsible for trunnion bearing load changes.